Brain Areas Involved in Modulating the Immune Response Participating in Hypertension and Its Target Organ Damage

Brain-Splenic Immune System Interactions in Hypertension: Cellular and Molecular Mechanisms

Hypertension represents a major worldwide cause of death and disability, and it is becoming increasingly clear that available therapies are not sufficient to reduce the risk of major cardiovascular events. Various mechanisms contribute to blood pressure increase: neurohormonal activation, autonomic nervous system imbalance, and immune activation. Of note, the brain is an important regulator of blood pressure levels; it recognizes the peripheral perturbation and organizes a reflex response by modulating immune system and hormonal release to attempt at restoring the homeostasis. The connection between the brain and peripheral organs is mediated by the autonomic nervous system, which also modulates immune and inflammatory responses. Interestingly, an increased autonomic nervous system activity has been correlated with an altered immune response in cardiovascular diseases. The spleen is the largest immune organ exerting a potent influence on the cardiovascular system during disease and is characterized by a dense noradrenergic innervation. Taken together, these aspects led to hypothesize a key role of neuroimmune mechanisms in the onset and progression of hypertension. This review discusses how the nervous and splenic immune systems interact and how the mechanisms underlying the neuroimmune cross talk influence the disease progression.

Hypertension-mediated organ damage involving multiple sites is an independent risk factor for cardiovascular events

Aims

Chronic pressure overload determines functional and structural alterations, leading to hypertension-mediated organ damage (HMOD), affecting multiple districts. We aim at evaluating the prognostic impact of the absence vs. presence of HMOD in one or more sites and of blood pressure (BP) and metabolic control in hypertensive patients.

Methods and results

The study included 7237 hypertensive patients from the Campania Salute Network Registry, followed up for 5.3 ± 4.5 years. As HMOD, we analysed the presence of left ventricular hypertrophy, carotid plaques, and chronic kidney disease (CKD-EPI ≥3 stage) and evaluated the impact of zero vs. one vs. two vs. three sites of HMOD on the occurrence of major adverse cardiovascular events (MACEs). Blood pressure control and Metabolic Score for Insulin Resistance (METS-IR) were also considered. Optimal BP control was achieved in 57.3% patients. Major adverse cardiovascular events occurred in 351 (4.8%) patients. The MACE rate in patients without HMOD was 2.7%, whereas it was 4.7, 7.9, and 9.8% in patients with one, two, and three sites with HMOD, respectively. By using Cox multivariate models, adjusted for age, BP control, mean heart rate, mean METS-IR, number of HMOD sites, and drugs, MACE was found to be significantly associated with ageing, mean METS-IR, anti-platelet therapy, and multiple sites with HMOD, whereas a negative association was found with renin-angiotensin system inhibitor drugs.

Conclusion

In hypertensive patients, the risk of MACE increases with the incremental number of districts involved by HMOD, independent of BP control and despite the significant impact of metabolic dysregulation. Hypertension-mediated organ damage involving multiple sites is the deleterious consequence of hypertension and dysmetabolism but, when established, it represents an independent cardiovascular risk factor for MACE occurrence.

The sustainable antihypertensive and target organ damage protective effect of transcranial focused ultrasound stimulation in spontaneously hypertensive rats

OBJECTIVE

In this study, we aimed to investigate the sustainable antihypertensive effects and protection against target organ damage caused by low-intensity focused ultrasound (LIFU) stimulation and the underlying mechanism in spontaneously hypertensive rats (SHRs) model.

METHODS AND RESULTS

SHRs were treated with ultrasound stimulation of the ventrolateral periaqueductal gray (VlPAG) for 20 min every day for 2 months. Systolic blood pressure (SBP) was compared among normotensive Wistar-Kyoto rats, SHR control group, SHR Sham group, and SHR LIFU stimulation group. Cardiac ultrasound imaging and hematoxylin-eosin and Masson staining of the heart and kidney were performed to assess target organ damage. The c-fos immunofluorescence analysis and plasma levels of angiotensin II, aldosterone, hydrocortisone, and endothelin-1 were measured to investigate the neurohumoral and organ systems involved. We found that SBP was reduced from 172 ± 4.2 mmHg to 141 ± 2.1 mmHg after 1 month of LIFU stimulation, P  < 0.01. The next month of treatment can maintain the rat's blood pressure at 146 ± 4.2 mmHg at the end of the experiment. LIFU stimulation reverses left ventricular hypertrophy and improves heart and kidney function. Furthermore, LIFU stimulation enhanced the neural activity from the VLPAG to the caudal ventrolateral medulla and reduced the plasma levels of ANGII and Aldo.

CONCLUSION

We concluded that LIFU stimulation has a sustainable antihypertensive effect and protects against target organ damage by activating antihypertensive neural pathways from VLPAG to the caudal ventrolateral medulla and further inhibiting the renin-angiotensin system (RAS) activity, thereby supporting a novel and noninvasive alternative therapy to treat hypertension.

Regulatory mechanism of immune-related genes in patients with hypertension

Hypertension (HT) is among the most common cardiovascular diseases in the world and is an important risk factor for stroke, myocardial infarction, heart failure, and kidney failure. Recent studies have demonstrated that activation of the immune system plays an important role in the occurrence and maintenance of HT. Thus, this research aimed to determine the immune-related biomarkers in HT. In this study, RNA sequencing data of the gene expression profiling datasets (GSE74144) were downloaded from the Gene Expression Omnibus database. Differentially expressed genes between HT and normal samples were identified using the software limma. The immune-related genes associated with HT were screened. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed using the program "clusterProfiler" of the R package. The protein-protein interaction network of these differentially expressed immune-related genes (DEIRGs) was constructed based on the information from the STRING database. Finally, the TF-hub and miRNA-hub gene regulatory networks were predicted and constructed using the miRNet software. Fifty-nine DEIRGs were observed in HT. The Gene Ontology analysis indicated that DEIRGs were mainly enriched in the positive regulation of cytosolic calcium ions, peptide hormones, protein kinase B signaling, and lymphocyte differentiation. The Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that these DEIRGs were significantly involved in the intestinal immune network for IgA production, autoimmune thyroid disease, JAK-STAT signaling pathway, hepatocellular carcinoma, and Kaposi sarcoma-associated herpesvirus infection, among others. From the protein-protein interaction network, 5 hub genes (insulin-like growth factor 2, cytokine-inducible Src homology 2-containing protein, suppressor of cytokine signaling 1, cyclin-dependent kinase inhibitor 2A, and epidermal growth factor receptor) were identified. The receiver operating characteristic curve analysis was performed in GSE74144, and all genes with an area under the curve of > 0.7 were identified as the diagnostic genes. Moreover, miRNA-mRNA and TF-mRNA regulatory networks were constructed. Our study identified 5 immune-related hub genes in patients with HT and demonstrated that they were potential diagnostic biomarkers for HT.

Therapeutic value of the metabolomic active neurotransmitter isorhynchophylline in the treatment of spontaneously hypertensive rats by regulating neurotransmitters

Hypertension is one of the most reported cardiovascular and cerebrovascular diseases with significantly high morbidity and mortality rates. This condition threatens the very existence of human beings. Numerous studies conducted earlier revealed the good therapeutic effect of isorhynchophylline on hypertension since the former regulates the metabolic disorders in neurotransmitters. However, the mechanism behind this action is yet to be deciphered. The current study followed the targeted metabolomics method to investigate the changes in the neurotransmitter level in the hippocampus of spontaneously hypertensive rats (SHRs) after the rats were treated with isorhynchophylline. The authors predicted the metabolic pathways involved in extensively modified neurotransmitters. Further, the expressions of metabolism-key enzymes in mRNA and protein levels were also determined. When treated with isorhynchophylline, it induced notably varying metabolomic profiles of the hippocampus in SHRs. Isorhynchophylline perturbed a total of seven extensively modified neurotransmitters as well as the primarily related pathways such as tyrosine and glutamate metabolism. An increase in the key metabolic enzymes such as DDC, MAO, COMT, TH, and DβH was observed in the SHR group, whereas their levels decreased after treatment with isorhynchophylline. The expression of GAD67 established cross-current validity. So, isorhynchophylline has been proved to have potential therapeutic value to treat hypertension via tyrosine and glutamate metabolism in the hippocampus. Further, the current study also opened new ventures to further investigate the working mechanism of isorhynchophylline in hypertension.